1. Field of the Invention
The present invention relates to a machining tool and a method of changing tools thereof. In particular, the present invention relates to a machining center which can true or dress the outer peripheral surface of a grinding wheel concurrently with a grinding process. Further, the present invention relates to a machining center and a method of changing tools thereof, the machining center being improved to effectively remove chips and generated heat, during a process of grinding a workpiece with a grinding wheel, by directing a machining fluid, in the form of a jet, onto a machining area from an optimum position and in an optimum direction. The present invention further relates to a machining center and a method of changing the tools thereof, the machining center being improved to prevent rotation of a cutting tool when the cutting tool is mounted to the machining center.
2. Description of the Related Art
When a metallic workpiece is machined and, in particular, the workpiece is ground, with a tool provided in a machining center, it is essentially necessary to supply a machining fluid to a machining area in order to remove the heat generated in the machining area and to remove chips resulting from machining so as to promote smooth machining by the tool.
As a first prior art, WO99/59774 describes a machine tool with a conventional machining fluid supplying apparatus for supplying a machining fluid to a machining portion of a tool when a workpiece is machined with the tool which is detachably mounted to a spindle of the machine tool. The machining fluid supplying apparatus includes a fluid jet port at the distal end of a fluid supplying nozzle. The fluid supplying nozzle is mounted around a spindle head, which has a spindle, through a support rod and a support bracket so that the nozzle can be moved in both radial and circumferential directions relative to an axis of the spindle by respective moving means. Further, an automatic tool measuring device is mounted to the machine tool so that the diameter of the tool mounted to the spindle is measured to adjust the position of the fluid supplying nozzle of the machining fluid supplying apparatus in both radial and circumferential directions in response to the changes in the tool diameter.
As a second prior art, U.S. Pat. No. 4,619,078 discloses a grinder equipped with a protective hood. The grinder includes a hood for covering a grinding wheel mounted to a spindle. The hood supports a machining fluid supplying nozzle. The machining fluid supplying nozzle can rotate together with the hood in the circumferential directions around the spindle. The machining fluid supplying nozzle also can move in the radial directions about the spindle in accordance with the diameter of the grinding wheel to supply a machining fluid to a contact point between the grinding wheel and a workpiece. The machining fluid supplying nozzle rotates together with the hood to prevent the interference between the hood and the workpiece. A motor moves the nozzle with respect to the hood in accordance with a decrease in the diameter of the grinding wheel, due to wear, so that the supplying direction of the machining fluid can be adjusted.
As a third prior art, Japanese Examined Patent Publication (Kokoku) No. 3-35054 describes a tool changing apparatus of a machine tool. The tool changing apparatus includes tool storing means composed of a plurality of cartridges having a plurality of tool pots (tool sockets) for storing tools. A cartridge having a desired tool is indexed to a tool delivery position. Tool conveying means changes tools disposed at the tool delivery position with tools disposed at the tool exchanging position. Further, the tools are exchanged between the tool exchanging position and the spindle.
The first prior art involves the following problems. Although the machining fluid supplying nozzle can be positioned in both the radial and circumferential directions, the machining fluid supplying nozzle cannot be positioned over the entire periphery around the grinding wheel. Therefore, in the first prior art, the machining fluid supplying nozzle cannot always be positioned at the optimum position, depending on the shape of a workpiece.
The second prior art relates to a machining center which is exclusively dedicated to a grinding process such as a surface grinder, and essentially requires a structure having a protective hood for a grinding wheel. In consequence, when a tool is removably mounted to the spindle by automatic tool changing means as in a machining center, the hood hinders the automatic tool exchange. Furthermore, the hood hinders positioning of the machining fluid supplying nozzle over the entire periphery of the grinding wheel.
In the third prior art, only one tool can be transported at once for the tool exchange. Therefore, this prior art provides low efficiency in the tool exchange when a grinding wheel and a dresser for truing or dressing must be changed in-process, that is, in case that dressing of a tool is conducted during a grinding process.
The present invention is directed to solve the prior art problems, and to provide a machining center capable of truing or dressing an outer peripheral surface of a grinding wheel during a grinding operation, and a method of changing the tools thereof.
Another object of the present invention is to provide a machining center, and a method of changing the tools thereof, in which a rotating mechanism having no dead angle around a spindle and a linear movement mechanism for linearly moving the machining fluid supplying nozzle in a radial direction cooperate to move the machining fluid nozzle of the machining fluid supplying apparatus to the optimum position for supplying the machining fluid to the engagement area between a tool and a workpiece.
Another object of the present invention is to provide a machining center capable of more efficiently exchanging tools, and a method of changing the tools thereof.
The invention described in claim 1 provides a machining center for machining a workpiece by moving a grinding wheel and the workpiece relative to each other, in the X, Y and Z directions, comprising a main spindle for removably mounting a grinding wheel; a spindle head for rotationally supporting the main spindle; a table for mounting the workpiece; a column for movably supporting the spindle head; and tool dressing means having a dresser spindle, provided over the spindle head, to move in the vertical direction toward and away from the grinding wheel mounted to the main spindle, for mounting a dresser for truing or dressing the outer peripheral surface of the grinding wheel.
According to the invention of claim 1, the dresser spindle can be lifted and lowered relative to the grinding wheel. Therefore, the machining center of the invention can execute a dressing or truing operation for the grinding wheel during a grinding operation, as an in-process operation.
According to another feature of the invention, there is provided a machining center for machining a workpiece by moving a grinding wheel and the workpiece relative to each other in the X, Y and Z directions, comprising a main spindle for removably mounting a grinding wheel; a spindle head for rotationally supporting the main spindle; a table for mounting the workpiece; a column for movably supporting the spindle head; tool dressing means having a dresser spindle, provided over the spindle head, to move in the vertical direction toward and away from the grinding wheel mounted to the main spindle, for mounting a dresser for truing or dressing the outer peripheral surface of the grinding wheel; and machining fluid supplying means including a machining fluid source and a machining fluid nozzle, for directing a machining fluid from the machining fluid source to a dressing area where the grinding wheel and the dresser engage with each other, the machining fluid nozzle being provided for advancing and retreating in an axial direction of the dresser spindle of the tool dressing means.
According to another feature of the invention, there is provided a machining center for machining a workpiece by moving a grinding wheel and the workpiece relative to each other in the X, Y and Z directions, comprising a main spindle for removably mounting a grinding wheel; a spindle head for rotationally supporting the main spindle; a table for mounting the workpiece; a column for movably supporting the spindle head; tool dressing means having a dresser spindle, provided over the spindle head, to move in the vertical direction toward and away from the grinding wheel mounted to the main spindle, for mounting a dresser for truing or dressing the outer peripheral surface of the grinding wheel; machining fluid supplying means including a machining fluid source and a machining fluid nozzle, for directing a machining fluid from the machining fluid source to a dressing area where the grinding wheel and the dresser engage with each other; cylindrical supporting means, disposed around the main spindle, for movably supporting the machining fluid nozzle of the machining fluid supplying means; radially moving means for linearly or rotationally moving the machining fluid nozzle of the machining fluid supplying means which is supported by the cylindrical supporting means to position the machining fluid nozzle in a radial direction relative to the grinding wheel; and circumferentially moving means for rotating the cylindrical supporting means to position the machining fluid nozzle of the machining fluid supplying means at any angular position around the grinding wheel.
According to another feature of the invention, there is provided a machining center for machining a workpiece by moving a grinding wheel and the workpiece relative to each other in the X, Y and Z directions, comprising a main spindle for removably mounting a grinding wheel; a spindle head for rotationally supporting the main spindle; a table for mounting the workpiece; a column for movably supporting the spindle head; tool dressing means having a dresser spindle, provided over the spindle head, to move in the vertical direction toward and away from the grinding wheel mounted to the main spindle, for mounting a dresser for truing or dressing the outer peripheral surface of the grinding wheel; machining fluid supplying means including a machining fluid source and a machining fluid nozzle, for directing a machining fluid from the machining fluid source to a dressing area where the grinding wheel and the dresser engage with each other, the machining fluid nozzle being provided for advancing and retreating in an axial direction of the dresser spindle of the tool dressing means; cylindrical supporting means, disposed around the main spindle, for movably supporting the machining fluid nozzle of the machining fluid supplying means; radially moving means for linearly or rotationally moving the machining fluid nozzle of the machining fluid supplying means which is supported by the cylindrical supporting means to position the machining fluid nozzle in a radial direction relative to the grinding wheel; and circumferentially moving means for rotating the cylindrical supporting means to position the machining fluid nozzle of the machining fluid supplying means at any angular position around the grinding wheel.
According to another feature of the invention, there is provided a machining center for machining a workpiece by moving a grinding wheel and the workpiece relative to each other in the X, Y and Z directions, comprising a main spindle for removably mounting a grinding wheel; a spindle head for rotationally supporting the main spindle; a table for mounting the workpiece; a column for movably supporting the spindle head; machining fluid supplying means including a machining fluid source and a machining fluid nozzle, for directing a machining fluid from the machining fluid source to a dressing area where the grinding wheel and the dresser engage with each other; a nozzle magazine, disposed on the table, for accommodating a plurality of the machining fluid nozzles; and the machining fluid nozzles being changed, between the spindle and the nozzle magazine, by the relative movement of the spindle and the table in the X, Y and Z directions.
According to another feature of the invention, there is provided a machining center for machining a workpiece by moving a grinding wheel and the workpiece relative to each other in the X, Y and Z directions, comprising a main spindle for removably mounting a grinding wheel; a spindle head for rotationally supporting the main spindle; a table for mounting the workpiece; a column for movably supporting the spindle head; tool dressing means having a dresser spindle, provided over the spindle head to move in the vertical direction toward and apart from the grinding wheel mounted to the main spindle, for mounting a dresser for truing or dressing the outer peripheral surface of the grinding wheel; tool accommodating means for storing a plurality of grinding wheels and dressers, the grinding wheels and dressers being mounted through tool pots; tool conveyer means for transporting the grinding wheel and the dresser held, the tool conveyer means having a rotatable tool holding arm for holding the grinding wheel or the dresser together with the tool pot, tool conveyer means rotating by 90 degrees to transport the grinding wheel or the dresser held by the tool holding arm between a tool delivery position and a tool exchanging position in the tool storing means; and tool changing means for exchanging the grinding wheel and the dresser which have been transported by the tool conveyer means to the tool exchanging position with the grinding wheel mounted to the spindle and the dresser mounted to the dresser spindle, respectively.
According to another feature of the invention, there is provided a method of changing tools in a machining center, the machining center including a main spindle for removably mounting a grinding wheel, a spindle head for rotationally supporting the main spindle, a table for mounting the workpiece, a column for movably supporting the spindle head, and tool dressing means having a dresser spindle, provided over the spindle head to move in the vertical direction toward and away from the grinding wheel mounted to the main spindle, for mounting a dresser for truing or dressing the outer peripheral surface of the grinding wheel, the method comprising the steps of: (a) storing a plurality of the grinding wheels and a plurality of the dressers in tool storing means with tool pots; (b) holding grinding wheel and the dresser stored in the tool storing meals together with the tool pot by a tool holding arm of tool conveyer means; (c) rotating by 90 degrees the tool conveyer means to transport the grinding wheel and the dresser held by the tool holding arm from a tool delivery position in the tool storing means to a tool exchanging position; (d) lifting the dresser spindle of the tool dressing means to change, with the tool changing means, the grinding wheel transported to the tool exchanging position with the grinding wheel mounted to the spindle; (e) rotating by 180 degrees the tool holding arm of the tool conveyer means, with the grinding wheel and the dresser, by the tool holding arm holds; (f) lowering the main spindle to change the dresser transported to the tool exchanging position with the dresser mounted to the dresser spindle by the tool changing means; (g) rotating the tool conveyer means by over 90 degrees to transport the used grinding wheel and the used dresser from the tool exchanging position to the tool delivery position; and (h) storing the used grinding wheel and the used dresser conveyed, together with the tool pot, in the tool delivery position in the tool storing means.
According to another feature of the invention, there is provided a machining center for machining a workpiece by moving a grinding wheel and the workpiece relative to each other in the X, Y and Z directions, comprising a main spindle for removably mounting a grinding wheel; a spindle head for rotationally supporting the main spindle; a table for mounting the workpiece; a column for movably supporting the spindle head; tool storing means for storing a plurality of the grinding wheels and the dressers with tool pots fitted to the grinding wheels and the dressers; tool conveyer means for transporting the grinding wheel and the dresser held, the tool conveyer means having a rotatable tool holding arm for holding the grinding wheel or the dresser together with the tool pot, tool conveyer means rotating 90 degrees to transport the grinding wheel or the dresser held by the tool holding arm between a tool delivery position and a tool exchanging position in the tool storing means; and tool changing means for exchanging the grinding wheel and the dresser which have been transported by the tool conveyer means to the tool exchanging position with the grinding wheel mounted to the spindle and the dresser mounted to the dresser spindle, respectively.